A: The river is much higher then the ground.

这条河比地还高。

B: How dangerous!

太危险了!

A: Yes, it is.

是的，很危险。

B: What if the river overflowed it’s bank?

如果河水溢上岸了怎么办?

A: That would be disastrous.

那将会是灾难。

B: The whole city will get flooded?

整个城市将被水淹。

A: Of course. But that happens only once in a blue moon.

当然，不过那几百年也不见得会遇上一次。